ALTERATIONS IN AUXIN AND CYTOKININ METABOLISM OF HIGHER-PLANTS DUE TOEXPRESSION OF SPECIFIC GENES FROM PATHOGENIC BACTERIA - A REVIEW

This review deals with the physiological and morphological effects of altering the auxin/cytokinin balance in transgenic plants by expressin g specific genes from pathogenic bacteria. Genes which have been used to alter auxin levels or sensitivity in transgenic plants include the iaaM/iaaH genes from Agrobacterium tumefaciens and A. rhizogenes; gene 5 and possibly gene 6b from A. tumefaciens; the rol B and possibly th e rol A gene from A. rhizogenes and the iaaL gene from Pseudomonas syr ingae subsp. savastanoi (P. savastanoi). Genes which have been used to alter cytokinin levels in transgenic plants include the ipt gene from A. tumefaciens and the rol C gene from A. rhizogenes. A variety of bi ochemical mechanisms have been identified which result in alterations to phytohormone levels following expression of these genes in transgen ic plants. Many of the effects on plant development are consistent wit h observations made following exogenous auxin and/or cytokinin applica tion to plant tissues, and the availability of these genes offers a ne w approach to the study of plant physiology using transformation metho dology.